U.S. Pat. No. 5,629,660 issued to Kenyon, et al. discloses a magnetic circuit and spring resulting in proportional control of the plunger. The patent to Kenyon, et al. does not, however, disclose a top cover and a coil can cover and a gap therebetween. The invention of Kenyon, et al. is directed toward use in heat transfer systems.
The present invention is for use with low pressure natural gas and propane and other similar materials. Specifically, the present invention is directed toward a systems which may operate as low as 0.25 psig. Typically, the present invention will see pressures in the range of 0.25 psig to perhaps 2.0 psig.